Influence of silica nanocoating on stain susceptibility and superficial integrity of dimethacrylate-based composites

The aim of this study was to investigate the ability of a novel silica (SiO₂ )-based nanocoating approach to extend the superficial integrity of current composites. Cylindrical discs (7 × 2 mm) were produced from nanohybrid and nanofilled composites. Specimens in control groups were not coated, but SiO₂ nanocoating was performed on specimens in experimental groups (n = 8). Specimens were stored for 24 h in distilled water at 37°C (baseline) and then artificially aged for 15, 90, or 180 d in a low-pH staining solution. Surface roughness (Ra) was measured using a profilometer, and a goniometer was used to determine surface free energy (SFE). Color change was evaluated by a reflectance spectrophotometer, applying the color distance metric, ΔE₀₀ , according to the Commission Internationale de l'Eclairage (CIE) L*a*b* coordinates. Data were subjected to repeated-measures anova and the Tukey post-hoc test. Composites presented visually perceptible color changes (ΔE₀₀  > 0.81) as early as 15 d of aging, with significantly higher ΔE₀₀ values recorded over time. Nanocoating with SiO₂ significantly reduced the SFE of composites at all storage times, and significantly lower Ra values were identified after aging. Nanohybrid and nanofilled composites were susceptible to substantial hydrolytic superficial degradation and staining, which was dramatically attenuated by the proposed SiO₂ nanocoating approach. Nanocoating effectively lowered the SFE of composites, thus minimizing water-composite interactions, which contributed to reduced superficial deterioration and lower stain susceptibility over time.